Internal combustion engine having concentric camshaft and balance shaft

ABSTRACT

An internal combustion engine, including a piston, a cylinder, and an output shaft, wherein the piston is arranged for reciprocating motion within the cylinder, driven by combustion, and the piston is coupled to the output shaft by a coupling such that said reciprocating motion of the piston drives rotation of the output shaft, wherein the coupling includes a connecting rod coupled to the piston, a slider bearing located for reciprocating movement relative to the connecting rod, the coupling further including a crankshaft rotatably mounted within a slider bearing, the engine having a camshaft and a balance shaft wherein the balance shaft is housed in a hollow of the camshaft such that the camshaft and the balance shaft rotate about a common axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage application under 35 U.S.C. §371 of International Application PCT/AU2020/051177, filed Oct. 29, 2020,which claims the benefit of priority to Application AU 2019904076, filedOct. 29, 2019. Benefit of the filing date of each of these priorapplications is hereby claimed. Each of these prior applications ishereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to an internal combustion engine. Moreparticularly, but not exclusively, the invention relates to an internalcombustion engine with piston motion characteristics leading to improvedperformance.

BACKGROUND OF THE INVENTION

It is known to provide an internal combustion engine for powering itemssuch as a vehicle, generator, machinery or the like. Traditionalconventional internal combustion engines use a crankshaft, crankpins andconnecting rods. However the applicant has identified that there arelimitations in noise, smoothness, efficiency and emissions ofconventional internal combustion engines.

Examples of the present invention seek to avoid or at least amelioratethe disadvantages of existing internal combustion engines.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided an internal combustion engine, including a piston, a cylinder,and an output shaft, wherein the piston is arranged for reciprocatingmotion within the cylinder, driven by combustion, and the piston iscoupled to the output shaft by a coupling such that said reciprocatingmotion of the piston drives rotation of the output shaft, wherein thecoupling includes a connecting rod coupled to the piston, a sliderbearing located for reciprocating movement relative to the connectingrod, the coupling further including a crankshaft rotatably mountedwithin a slider bearing, the engine having a camshaft and a balanceshaft wherein the balance shaft is housed in a hollow of the camshaftsuch that the camshaft and the balance shaft rotate about a common axis.

Preferably, the connecting rod is a unitary connecting rod.

In a preferred form, the balance shaft is driven at the same speed as aspeed of the crankshaft.

Preferably, the engine is provided with a single balance shaft.

Preferably, the camshaft rotates at half the speed of the crankshaft.

The camshaft and balance shaft may be pre-assembled as a module prior toassembly in the engine.

In accordance with another aspect of the present invention, there isprovided an internal combustion engine, including a piston, a cylinder,and an output shaft, wherein the piston is arranged for reciprocatingmotion within the cylinder, driven by combustion, and the piston iscoupled to the output shaft by a coupling such that said reciprocatingmotion of the piston drives rotation of the output shaft, wherein thecoupling includes a connecting rod coupled to the piston, the enginehaving a camshaft and a balance shaft wherein the balance shaft ishoused in a hollow of the camshaft such that the camshaft and thebalance shaft rotate about a common axis.

There is also disclosed an internal combustion engine, including apiston, a cylinder, and an output shaft, wherein the piston is arrangedfor reciprocating motion within the cylinder, driven by combustion, andthe piston is coupled to the output shaft by a coupling such that saidreciprocating motion of the piston drives rotation of the output shaft,the coupling being arranged such that the piston has sinusoidal motionfor constant rotational velocity of the output shaft (or when plottedagainst rotational angle of the output shaft).

Preferably, the engine is in the form of a scotch yoke engine.

In a preferred form, the coupling includes a slider bearing. Morepreferably, the engine includes a pair of opposed pistons which aremutually rigidly fixed.

Preferably, the engine is arranged such that, when measured against aconventional crankshaft engine of identical bore and stroke, the motionof the piston after top dead centre has a lower acceleration such thatvolumetric difference in the cylinder, when compared to the conventionalcrankshaft engine, peaks at between 10% and 20% between top dead centreand bottom dead centre.

More preferably, the engine is arranged such that, when measured againsta conventional crankshaft engine of identical bore and stroke, themotion of the piston after top dead centre has a lower acceleration suchthat volumetric difference in the cylinder peaks at between 15% and 17%between top dead centre and bottom dead centre.

Even more preferably, the engine is arranged such that, when measuredagainst a conventional crankshaft engine of identical bore and stroke,the motion of the piston after top dead centre has a lower accelerationsuch that volumetric difference in the cylinder peaks at between 40 and80 degrees of output shaft rotation after top dead centre.

In one form, the engine is arranged such that, when measured against aconventional crankshaft engine of identical bore and stroke, the motionof the piston after top dead centre has a lower acceleration such thatvolumetric difference in the cylinder peaks at between 50 and 70 degreesof output shaft rotation after top dead centre.

It is preferred that the engine is arranged, such that, when measuredagainst a conventional crankshaft engine of identical bore and stroke,the motion of the piston after top dead centre has a lower accelerationsuch that volumetric difference in the cylinder peaks at between 50 and60 degrees of output shaft rotation after top dead centre.

In one form, the engine includes a combustion chamber, and thecombustion chamber and/or the coupling is/are arranged to achieve goalvolumetric difference characteristics, when compared to a conventionalcrankshaft engine.

There is also disclosed a method of manufacturing an engine as describedabove, including:

-   -   measuring and/or modelling charge density in the cylinder to        obtain data; and    -   using said data to optimise one or more parameter(s) of the        engine so as to increase maintenance of a gas state with a        higher charge density around top dead centre.

Preferably, the method includes the step of using said data to optimiseone or more parameter(s) of the engine, said parameter(s) including oneor more of the coupling, the piston, the cylinder, a combustion chamber,and valves.

More preferably, the method includes the step of using said data tooptimise one or more parameter(s) of the engine so as to increasemaintenance of a gas state with a higher charge density around top deadcentre to achieve improved fuel mixing.

Preferably, the slider bearing is formed of separable parts which abuttogether at an interface which is diagonal to an axis of slidingmovement of the slider bearing. More preferably, the separable partseach have a mating face which abut along said interface. The mating facemay terminate at an upper surface of the slider bearing and at a lowersurface of the slider bearing.

In a preferred form, the separable parts are coupled together by atleast one fastener which extends along an axis which is diagonal to anaxis of sliding movement of the slider bearing. More preferably, saidfastener is accessed through a surface of the slider bearing which isperpendicular to an axis of sliding movement of the slider bearing. Evenmore preferably, the separable parts are coupled together by a pair offasteners, with one fastener being accessed through an upper surface ofthe slider bearing and the other fastener being accessed through a lowersurface of the slider bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of non-limiting example onlywith reference to the accompanying drawings, in which:

FIG. 1 shows a perspective view of an engine in accordance with anexample of the present invention;

FIG. 2 shows a graph of piston velocity of an engine in accordance withan example of the present invention against motion of a piston of aconventional engine, before and after zero velocity at top dead centre;

FIG. 3 shows a graph depicting total working unit cylinder volume versuscrank angle for an engine in accordance with an example of the presentinvention as well as for a conventional engine;

FIG. 4 shows modelling results of an engine in accordance with anexample of the present invention;

FIGS. 5 to 17 show tables and diagrams to explain advantages of aninternal combustion engine in accordance with an example of the presentinvention, over a conventional internal combustion engine;

FIG. 18 shows a diagram illustrating a combined concentric camshaft andbalance shaft;

FIGS. 19 to 28 show diagrams pertaining to an angled slider block, anoil pump arrangement, piston sprays and a lubrication circuit;

FIGS. 29 to 31 show diagrams of a two-stage blow-off valve and ablow-off (intermediate) regulator;

FIGS. 32 to 35 depict a guide shoulder arrangement;

FIGS. 36 and 37 show a crank assembly in isometric and exploded views;

FIGS. 38 and 39 show a crank, slider blocks and conrods assembly inisometric and exploded views;

FIG. 40 shows an exploded view of the internal combustion engineincluding an intake system; and

FIG. 41 shows a diagrammatic representation of a cyclonic air flow in aplenum chamber by virtue of the arrangement of the intake system.

DETAILED DESCRIPTION

FIGS. 1 to 4 depict operation of an internal combustion engine inaccordance with an example of the present invention.

More specifically, in accordance with an example of the presentinvention, the applicant has developed an internal combustion engine 10,including a cylinder 12, a piston 14 (also reference numeral 92 in FIG.5 ), and an output shaft 16, wherein the piston 14 is arranged forreciprocating motion within the cylinder 12, driven by combustion, andthe piston 14 is coupled to the output shaft 16 by a coupling. Theengine 10 is configured such that said reciprocating motion of thepiston 14 drives rotation of the output shaft 16. The coupling isarranged such that the piston 14 has sinusoidal motion when plottedagainst rotational angle of the output shaft 16.

In the example depicted in the drawings, the engine 10 is in the form ofa scotch yoke engine, as shown in FIG. 1 , and the coupling includes aslider bearing 90 (or slider block) which is able to slide along achannel formed between opposed connecting rods 86. The engine 10 of theexample includes a pair of opposed pistons 14 which are mutually rigidlyfixed such that movement of one piston in a first direction causesmovement of the other piston in a second direction which is opposite tothe first direction (see also pistons 92 in FIG. 5 ).

With reference to FIGS. 2 and 3 , the engine 10 is arranged such that,when measured against a conventional crankshaft engine of identical boreand stroke, the motion of the piston 14 after top dead centre (“TDC”)has a lower displacement, velocity and acceleration such that volumetricdifference in the cylinder 12, when compared to the conventionalcrankshaft engine, peaks at between 10% and 20% between TDC and bottomdead centre (“BDC”). In FIG. 2 , velocity of the piston 14 of the engine10 according to an example of the present invention is shown by line 18,whereas velocity of a piston of a conventional engine having identicalbore and stroke (to engine 10) is shown by line 20. In FIG. 3 , TotalWorking Unit Cylinder Volume of the engine 10 according to an example ofthe present invention is shown by line 22, whereas Total Working UnitCylinder Volume of a conventional engine having identical bore andstroke (to engine 10) is shown by line 24. With regard to FIG. 3 ,motion of the piston 14 is sinusoidal such that velocity of the piston14 is greater around TDC 26 (than for a conventional engine) whereasvelocity of the piston 14 is less around BDC 28 (than for a conventionalengine).

Looking specifically at FIG. 3 , the engine 10 is arranged such that,when measured against a conventional crankshaft engine of identical boreand stroke, the motion of the piston 14 after TDC 26 has a loweracceleration such that volumetric difference in the cylinder 12 peaks atbetween 15% and 17% between TDC 26 and BDC 28. In the example shown, theengine 10 is arranged such that, when measured against a conventionalcrankshaft engine of identical bore and stroke, the motion of the piston14 after TDC 26 has a lower acceleration such that volumetric differencein the cylinder 12 peaks at between 40 and 80 degrees of output shaftrotation after TDC 26. This peak may, more specifically, be between 50and 70 degrees of output shaft rotation after TDC. Even morespecifically, this peak may be between 50 and 60 degrees of output shaftrotation after TDC 26.

The engine 10 includes a combustion chamber 30 for combustion of thecharge, and the combustion chamber 30 and/or the coupling is/arearranged to achieve goal volumetric difference characteristics, whencompared to a conventional crankshaft engine.

The applicant has, advantageously, identified a method of manufacturing(and, specifically, designing) an engine 10, the method including thesteps of measuring and/or modelling charge density in the cylinder 12 toobtain data; and using the data to optimise one or more parameter(s) ofthe engine 10 so as to increase maintenance of a gas state with a highercharge density around TDC 26. The method may include the step of usingthe data to optimise one or more parameter(s) of the engine 10, theparameter(s) including one or more of the coupling, the piston 14, thecylinder 12, the combustion chamber 30, and valves 32.

The method may include the step of using the data to optimise one ormore parameter(s) of the engine 10 so as to increase maintenance of agas state with a higher charge density around TDC 26 to achieve improvedfuel mixing.

As discussed above, with reference to FIG. 3 , movement of the piston 14in the engine 10 is sinusoidal. The movement of the piston 14 againstcrank angle over top dead centre 26 and bottom dead centre 28 areidentical, as shown by the sinusoidal curve of line 22 in FIG. 3 .

In contrast, the crank and connecting rod mechanism of conventionalengines produces unequal piston movement in the region of TDC 26 and BDC28 (see line 24 in comparison to line 22). In the region of TDC 26 thepiston of the conventional engine moves faster than in the engine 10 ofpresent invention and, in the region of BDC 28, the piston of theconventional engine moves slower than in the engine 10 of the presentinvention. For a given engine stoke the difference between these twoconditions depends on the length of a con rod. The shorter the con rod,the greater the differences.

The power level for a given piston displacement is very much a functionof the amount of air mass captured per cycle affecting the enginevolumetric efficiency. Volumetric efficiency depends on several enginedesign parameters, namely; cam profile, valve timing, manifold tunedlength, forced air induction (Turbo/Supercharging) etc. which areoptimised for the pressure wave dynamics set by any given piston motion.Therefore, the processes that will be influenced by piston motion can bedivided into two categories; induction process and post inductionprocesses.

The present invention focusses on the post induction processes ie.:compression, combustion and expansion, being influenced by the pistonmotion. The applicant has identified that it is of particular interestto note the production of NOx emissions in the combustion processes andthe expansion stroke (post combustion) when the useful work is produced.In order to understand the advantages of the engine 10 of the presentinvention and, in particular, the advantage of the motion of the piston14 over that of a conventional engine we must first compare an identicalvolumetric efficiency and piston bore and stroke to have identicalinduction conditions for both the engine 10 of the present invention anda conventional engine.

In the graph shown in FIG. 2 , two engines of differing piston motionbut otherwise identical in other respects (with identical volumetricefficiency and identical bore and stroke) were compared under the sameengine speed, load (full power) and air-fuel ratio.

Piston velocity in this unit (mm/degree crank) is independent of enginespeed and hence is characteristic of piston motion over the entire speedrange. Clearly, the piston 14 of the engine 10 approaches and goes awayfrom TDC 26 at a lower acceleration (rate of change of velocity) thanthe conventional piston. This means the engine 10 will have a lower rateof cylinder volume change around TDC 26 and therefore will help maintaina gas state with higher charge density around TDC 26. The applicant hasidentified that a higher charge density assists the flame to speed up.The lower piston acceleration extends over a considerable part of thegas expansion duration.

When computed over the entire speed range, the cylinder peak pressuresare found to be lower in the engine 10 than in the conventional enginein most speeds except for the lower speeds of 1500 and 2500 r/min wherethe peak pressures are very similar. However, cylinder pressure duringthe gas expansion process (i.e. after mass fraction burned has reached1.0) remains higher in the engine 10 compared with that in theconventional engine providing more useful work (and a higher IMEP) forthe engine 10.

The subject of combustion needs far deeper treatment due to othercomplex engine related parameters, ie: squish velocity (including thegeometry of the squish surfaces) and heat losses through surface(influenced by combustion chamber geometry, piston-con rod connectionresponsible for uniformity of temperature of piston crown around thejoint face, cooling water circuit, etc.). But importantly, all of thesecontribute to the development of the resultant cylinder pressure(profile) which is responsible for the power level and emissions thatare achieved.

As shown in FIG. 4 , there are shown modelling results of the engine 10according to an example of the present invention, depicting the nearperfect airflow tumble as it enters and fills the cylinder 12 resultingin homogenous fuel mixing giving cleaner combustion, high torque andlower emissions.

The piston 14 approaches and goes away from TDC 26 at a loweracceleration than the conventional piston with both engines havingidentical stroke and bore. This means the engine 10 will have a lowerrate of cylinder volume change around TDC 26 and the applicant hasidentified that this helps maintain a gas state with higher chargedensity around TDC 26, leading to homogenous fuel mixing resulting incleaner combustion, more engine knock resistance, high EGR tolerance,high torque and lower emissions.

In one example, the applicant has identified that the engine 10 may beused to drive a generator in a hybrid vehicle. More specifically, theapplicant has identified that the engine 10 may be used to drive agenerator in a series hybrid vehicle, possibly with the engine beingoperated at constant rotational velocity during running of the generatorwhich may be located in a discrete location of the vehicle, such as inthe boot/trunk. The efficiency, balance, low vibration and quietness ofthe engine 10 may make the engine 10 particularly suitable to such anapplication.

Targeted Engine Lubrication and Oil Pump Arrangement

In many traditional engines, oil pressure is generated by an oil pumpdriven by the crankshaft. When excess oil pressure and flow is achievedby the oil pump at higher engine speeds, this excess oil is redirectedby a pressure regulating device back into the suction port of the pumpor back to the sump via an exhaust passage. Normally, in a rangeextender engine, when the engine is at low engine speeds, the engine haslow oil pressure but is also at low load. When the engine speed isincreased, so too is the load and correspondingly the oil pressure andflow is also increased to a point where the pump generates excess oilthat is not normally used and is redirected back to the engine sump orback to the pump suction port.

With reference to FIGS. 19 to 31 , the following invention, outlinesseveral methods of targeting lubrication to the areas of an engine thatneed it most and a method of using this excess oil to the advantage ofthe engine by redirecting this excess oil in the first case to otherareas of the engine and then if the pump still has excess oil available,only then would the oil be redirected back to the suction port of thepump or to the sump.

This aspect of the patent specification covers the following key areas:

-   -   The use of an angled slider block and bearing to cause an        uninterrupted slider bearing face    -   The direct deposition of bearing-type material onto the        uninterrupted slider bearing face of the slider block    -   A two stage regulator in the pump lube circuit that has a        primary and secondary relief function whereby the primary relief        creates oil pressure and flow that is targeted at specific areas        of the engine in high engine load situations    -   Targeted piston cooling using spray jets on the slider block    -   Targeted piston cooling using primary relief oil from the        regulator via spray jets inside the engine    -   Targeted piston cooling using slider bearing excess oil via        spray jets on the connecting rod    -   Unique controlled lubrication from the shell bearings to the        side faces of the slider block using notches or impressions or        controlled surface finishes and leakage    -   A pre-set regulator in the lube circuit that redirects oil that        is targeted at specific areas of the engine in high engine load        situations

The result is:

-   -   Less wastage of oil from the oil pump    -   A controlled re-direction of normally wasted oil to critical        areas of the engine where it can be of benefit    -   Less oil foaming    -   Improved engine efficiency    -   Improved engine performance    -   Piston cooling    -   A reduction in friction as targeted lubrication can result in        smaller bearing surfaces

In addition, the use of a slider block in a scotch yoke engine requiresspecific targeted lubrication to maintain a boundary layer of oil on thesliding bearing surfaces.

With reference to FIG. 25 , piston sprays in engine block that are fedfrom excess oil from slider block. Slider block oil gallery aligns withspray nozzle and supplies oil to jet at the top and bottom of eachstroke (jets closed in this view). Turning to FIG. 26 , Piston Sprays inengine block that are fed from excess oil from slider block. Sliderblock oil gallery aligns with spray nozzle and supplies oil to jet atthe top and bottom of each stroke (top jet open in this view).

FIG. 27 shows notches in edge of bearing faces (6 shown) to allow oil toleak past the thrust face and out the side of the bearing to lubricatethe sides of the bearing and the associated thrust faces. This alsoapplies to the side of the crank flange guide faces.

Concentric Camshaft and Balance Shaft

In many traditional engines, a balance shaft is used to reduce enginevibration. These balance shafts spin at a speed relative to the engineand are driven by the crankshaft. This speed is normally twice enginespeed and in the case of a 4 cylinder in-line conventional engine twobalance shafts are required. These shafts act to dampen engine vibrationby inducing an imbalance opposite to the engine induced vibration,normally known as second order forces.

With reference to FIG. 18 , by virtue of the Sytech engine design,second order forces are minimal, thus only one balance shaft is requiredand this spins at engine speed, not twice engine speed. The followinginvention, outlines a balance shaft that is located inside the camshaftof an engine. For reference purposes, the camshaft spins at half enginespeed. This Concentric combined camshaft and balance shaft has manybenefits to the engine design including:

-   -   A reduction in the rotational inertia of the assembly could be        achieved if the camshaft and balance shaft spin in        contra-rotation    -   Space requirements are reduced as this invention allows the same        positioning of both the camshaft and the balance shaft within        the same assembly resulting in optimal packaging    -   The cost of the assembly is reduced as less machining of the        cylinder block is required    -   The camshaft and balance shaft can be pre-assembled as a module        prior to assembly in the engine    -   In V-type engines the valley between the cylinder heads can be        used for location of the combined camshaft/balance shaft        resulting in a smaller engine package and re-locating the        balance shaft out of the engine sump where normally it could        contribute to oil churning and foaming

The result is:

-   -   Less machining of cylinder block    -   Lower cost due to the use of lower cost bearings (differential        speed of parts is reduced)    -   A reduced alignment tolerance stack up for the cylinder block        resulting in a lower cost, easier to manufacture cylinder block    -   A reduction in friction previously caused by higher bearing        speeds of the balance shaft    -   Ease of assembly and lower assembly costs

In order to make best use of this invention, the camshaft and balanceshaft would spin in the same direction so as to minimise thedifferential bearing speeds between the parts.

Scotch Yoke Piston Connecting Rod and Crankshaft Guide

With reference to FIGS. 32 to 35 , the Sytech engine is an engine thatrelies on the Scotch Yoke principle of operation in a horizontal,opposed in-line cylinder arrangement. Typically, these engines requirevery close tolerance of the two opposing cylinders within the cylinderblock to ensure alignment and so as not to induce side load of thepiston or over-constraint and loading of the slider block on thecrankshaft. This results in very tight tolerances and manufacturing coston the:

-   -   Cylinder bores    -   Cylinder block    -   Crankshaft positioning    -   Reciprocating mechanism alignment

Conventional engines must have a rotating joint between the conrod andthe piston to allow for the conrod to follow the circular motion of thecrankshaft big-end journal. A Sytech engine does not normally need thisrotating joint as the pistons and connecting rod move only in a lineardirection and hence have no side forces.

In an effort to reduce manufacturing tolerance sensitivity and reducethe need for “matched” cylinder block halves, we wish to include afloating connection between the connecting rod and the piston andtransfer the guidance and alignment of the pistons from the cylinderbore to the crankshaft.

This means that:

-   -   the slider bearing will be guided on the crankshaft by use of        thrust collars    -   The slider bearing will be guided within the connecting rod by        use of a slider bearing and side thrust faces    -   The piston will be free to find its own centre within the        cylinder bore without being constrained by a fixed connection        between the piston and connecting rod

This will allow the piston bores within the cylinder block to betoleranced and aligned in reference to the crankshaft rather than to theopposing cylinder block. The pistons themselves will be free to centrethemselves within the cylinder bore via their own minimal, short pistonskirt without being held to positional tolerance by the connecting rod.The result is:

-   -   Fully floating pistons that operate according to Sytech        sinusoidal piston motion    -   Cylinder blocks that can be manufactured separately and not as a        matched pair    -   A reduced bore centre tolerance between opposite and adjacent        cylinders    -   A reduced alignment tolerance stack up for the cylinder block        and corresponding cylinder bores resulting in a lower cost,        easier to manufacture cylinder block    -   A reduction in friction previously caused by misalignment    -   Ease of assembly

Accordingly, the crankshaft 512 has a pair of opposed guide shoulders504 for locating at or near opposed sides of the slider bearing. Morepreferably, the shoulders 504 are spaced to provide a gap between theslider bearing and the shoulders 504. Even more preferably, the gap issufficient to allow relative movement of the slider bearing axiallybetween the shoulders 504 to allow the unitary connecting rod toself-centre relative to the crankshaft.

The engine may be provided with a pin coupling to accommodate boremisalignment. More preferably, the pin coupling accommodates twist inone or more directions. The pin coupling may accommodate crank to boremisalignment.

The shoulders 504 may be tapered radially outwardly to each have alarger inner radius facing the slider bearing. More specifically, theshoulders may be tapered outwardly toward the slider bearing so as toprovide a larger guide shoulder surface for abutment to limit movementrelative to the slider bearing.

In one form, the crankshaft may be provided with a lubrication passagedirected radially outwardly toward an inside surface of the sliderbearing.

Crank Mechanism Assembly

With reference to FIGS. 36 to 39 , there is shown an arrangement inwhich the connecting rods of the internal combustion engine are formedof two like parts, each of the like parts being in the form of anidentical C-claw. More specifically, there is shown an internalcombustion engine, including a pair of opposed pistons, a pair ofopposed cylinders, and an output shaft, wherein each of the pistons isarranged for reciprocating motion within a respective one of thecylinders, driven by combustion, and the pistons are coupled to theoutput shaft by a coupling such that said reciprocating motion of thepistons drives rotation of the output shaft. The coupling includes aconnecting rod coupled to the opposed pistons, the connecting rod beingformed from a pair of like parts 524, 526 fastened together, one 526 ofthe like parts being reversed relative to the other 524 of the likeparts prior to fastening.

The connecting rod may have side guides for guiding a slider bearinglocated for reciprocating movement relative to the connecting rod, andthe coupling may further include a crankshaft rotatably mounted withinthe slider bearing.

Cyclonic Airflow

With reference to FIGS. 40 and 41 , the Sytech engine may have an intakesystem 530 which promotes a cyclonic airflow in a plenum chamber so asto have an effect similar to a ram charging effect. In particular, thereis shown an internal combustion engine, including a pair of opposedpistons, a pair of opposed cylinders, and an output shaft, wherein eachof the pistons is arranged for reciprocating motion within a respectiveone of the cylinders, driven by combustion, and the pistons are coupledto the output shaft by a coupling such that said reciprocating motion ofthe pistons drives rotation of the output shaft, wherein the couplingincludes a connecting rod coupled to the opposed pistons, the connectingrod having side guides for guiding a slider bearing located forreciprocating movement relative to the connecting rod. The couplingfurther includes a crankshaft rotatably mounted within the sliderbearing. The internal combustion engine includes an intake system 530arranged to induce cyclonic airflow in a plenum chamber of the intakesystem.

The firing order of the cylinders may be 1-2-4-3. The intake system maybe arranged such that intake conduits leading to the cylinders meet atthe plenum chamber and are arranged generally in a circularconfiguration about the plenum chamber in the firing order of thecylinders. The intake conduits from the plenum chamber to the cylindersmay be arranged to promote free flow resulting from the cyclonic airflowin the plenum chamber. In one form, the intake conduits may be directedto capture flow from the cyclonic airflow in the plenum chamber. Inparticular, the intake conduits may lead tangentially from the plenumchamber so as to efficiently capture momentum of the cyclonic airflow.The plenum chamber may be located centrally in relation to the cylindersof the engine and this may be of particular advantage where the engineis a Scotch Yoke type engine as this may facilitate the centralplacement of the plenum chamber as well as the tuning of the lengths ofthe intake conduits. In one form, the intake conduits may each be ofequal length. By virtue of the cyclonic airflow in combination with theengine being of scotch yoke type, there is greater opportunity to shapethe plenum with an optimal shape such as, for example, a rounded and/orcircular shape.

The described construction has been advanced merely by way of exampleand many modifications and variations may be made without departing fromthe spirit and scope of the invention, which includes every novelfeature and combination of features herein disclosed.

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” and “comprising”, will be understood to imply the inclusionof a stated integer or step or group of integers or steps but not theexclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (orinformation derived from it), or to any matter which is known, is not,and should not be taken as an acknowledgment or admission or any form ofsuggestion that that prior publication (or information derived from it)or known matter forms part of the common general knowledge.

Benefits Associated with the Invention

The invention may be used in a wide variety of applications and, inparticular, as a low cost and unique solution for modern rangeextenders.

The inventors have developed a new family of modern opposed pistongasoline engines based on the Scotch Yoke Crankshaft connectionprinciple, called the SYTECH Engine. The engine family consists ofmodular 2 cylinder units that are joined together to create a family ofengines. Due to the engine construction, the engine can be modularizedin even numbers of cylinders, i.e, 2 cylinders, 4 cylinders, 8 cylindersetc. With this approach, common engine parts and architecture can beemployed to reduce engine cost and weight. This paper focusses primarilyon the first engine in the family, a 1.5 litre 4 cylinder engineidentified as the 415 engine, where 4 represents the number of cylindersand 15 represents the 1.5 l engine displacement. During the combustionsystem analysis phase, FEV was responsible for developing an optimizedcombustion chamber concept with a tailored set of engine geometryparameters which could best leverage the benefits of the Scotch YokePrinciple. In order to do this, 1D engine modelling software (GT-Power)and 3D Computational fluid dynamics software Star CCM+ were used toaccurately model the effect of the unique piston motion on the chosencombustion chamber concept respectively. Once this had been performedand the engine combustion modelled, the next step was to determine thenecessary technologies and associated costs when using the Scotch YokePrinciple to prepare the engine for future legislative and customerrequirements. This paper provides a brief overview of ASFT's new enginefamily with a focus on the detailed results of the combustion systemanalysis and engine recommendations leading to the prototype build phaseand the upcoming engine testing.

1 Introduction to the New Family of Modern SYTECH Engines

The background of the new engine family is the development of a commoncore engine structure in the crankshaft and piston connection that canbe applied to multiple engine configurations. This enables the engine tobe built to suit a wide range of power outputs with maximum commonalitywhile protecting for the application of additional technologies in thefuture. The benefits of this strategy are that it allows a wide range ofengine variants that achieve legislative compliance whilst using as manycommon parts as possible with the required technology package.

In order to determine the best architecture for the engine, we firstmodelled the engine construction. The SYTECH engine piston motion isuniquely different to traditional crank/connecting rod engines. Due tothe connecting rod arrangement, the SYTECH piston travels in a uniformway following a pure sinusoidal motion. FIG. 5 shows the SYTECHconnecting rod arrangement with the slider block.

A conventional engine has a piston motion that is quite short/sharp atthe top of the stroke during combustion, this is a function of therelationship between the connecting rod and crank throw length. TheSYTECH mechanism results in a pure sinusoidal piston motion regardlessof the connecting rod length as depicted in FIGS. 2 and 3 .

Although this difference appears to be minor, the net effect is that thecombustion process has more time to complete in the end of thecompression stroke. In theory this results in more time to burn thefuel, a more uniform piston motion, more uniform pistonpressures/forces, less firing force peaks and lower emissions.

The next advantage of the SYTECH piston arrangement is that two opposingpistons share the same crankshaft journal. This makes the engine muchshorter than conventional engines and traditional boxer engines. Whencomparing bore spacing alone and ignoring front and rear engineaccessories, a 4 cylinder SYTECH engine can be up to 50% shorter than atraditional In-line 4 cylinder engine. When comparing a 4 cylinderSYTECH opposed piston engine to a 4 cylinder boxer engine, the SYTECHengine is up to 33% shorter. This makes the SYTECH engine very easy topackage in most engine bays and offers advantages when packaging theengine in other areas of the vehicle like behind the rear seats, underthe vehicle etc.

FIG. 6 shows an engine length comparison of A (inline 4), B (Boxer 4)and C (Sytech 4).

The third advantage of the engine is that due to Scotch yoke mechanismand slider block arrangement, there are almost no out of balance forcesand very low piston side forces. This results in a well-balanced enginethat is quiet. FIG. 7 , out-of-balance force comparison, shows theSYTECH engine out of balance forces when compared to other engines. FIG.8 , NVH test results, shows the results of testing conducted on earlyprototypes of the engine developed several years ago. The NVH advantagesare highly evident in these results and this is key for Range ExtenderVehicles which are primarily a Battery Electric Vehicle with an on-boardgenerator. The generator needs to be quiet and vibration free so as tobe as unobtrusive as possible and not negatively impact on the comfortof the vehicle operator when it is running.

The advantages of the SYTECH engine make it an attractive solution forthe Range Extender market, so we decided that we would like to buildsome engines for testing, but only if the engine was able to meet thePerformance and Emission targets, especially those of the China marketand China 6b emissions.

The first step in designing an engine is to set targets for the engineperformance and to then model the engine, specifically in SYTECH's case,model the engine using the SYTECH piston motion along with the resultingcombustion in order to optimize the bore, stroke, compression ratio,valve sizes, valve overlap, valve timing and injector requirements tomeet the target performance and emission levels. Initial targetparameters were set for the engine design and analysis based on a 1.5 Llow cost, minimum technology package engine.

The key design parameters were;

-   -   An emission output that meets China 6b    -   RON 92 Fuel    -   A Normally Aspirated power rating of 60 kW at 4500 1/min    -   Best In Class Fuel Economy

The design process to be followed was aimed at coming up with acombustion system concept that enabled us to have a family of enginesthat are based on the same core internal design where all the engines inthe family would share the same bore, stroke, compression ratio, crankbearing diameter, connecting rod, piston, slider block, valvesizes/angles and be modular. The outputs would then be expected to besomething similar to that shown in the table of FIG. 9 , “Enginefamily”. This table shows variation in parameters, engine displacementand engine power estimate according to 2 cylinder, 4 cylinder and 8cylinder versions of the engine.

As a result, if successful, the three engine variants would share;

-   -   the same cylinder bore    -   the same combustion chamber    -   the same valve sizes    -   the same injector arrangement    -   the same piston    -   the same connecting rod    -   the same timing drive    -   the same slider block

and many of the other base engine components. This decreases productioncomplexity, increases common part volumes, improves reliability,decreases manufacturing/tooling and decreases overall engine cost.

2 SYTECH Combustion System Analysis

Conventional 4 cylinder engines have a firing order that is 1-3-4-2; incontrast, the SYTECH opposed piston engine has a firing order that is1-2-4-3. This change in firing order is not so important when modellingthe individual combustion chamber performance but is critical whenmodelling the Inlet manifold, the plenum chamber and the exhaust systemin order to determine the lengths and tuning of these inlet and exhaustsystems to optimize the final engine performance.

FIG. 10 shows that the firing order of the SYTECH engine is 1-2-4-3.

3 Combustion Assessment Via FEV's Charge Motion Design Process

The concept and layout phase of the new engine family was supported byFEV's charge motion design CFD process. This process analyses andcompares the geometries of the air guiding surfaces in the cylinder headand the combustion chamber to predict an optimal combination of engineparameters to achieve the design targets. It also considers theinteraction between the in-cylinder flow field and the fuel injectionfor improved and optimized fuel homogenization.

The concept study model was used to determine the optimum bore andstroke for the SYTECH engine. After several early runs in the model, theoptimum bore and stroke was determined to be 85 mm stroke and 75 mmbore, this gave us a 1.5 L 4 cylinder engine. Using a data drivenapproach, sufficient iterations of the model were then performed,modified and repeated to determine the optimum arrangement of thecombustion chamber.

After these modelling iterations, the engine architecture that wasdecided on moving forward was;

-   -   A 4 valve combustion chamber, 2 inlet and 2 exhaust without        camshaft phasers    -   A centrally placed spark plug    -   Port Fuel Injection (not DI)    -   A flat piston    -   11.0:1 compression

Further modelling iterations and analysis of the engine yielded valvesizes and angles that were the best match to the piston motion of theSYTECH Engine and were good inputs for the next stage of the enginemodelling. Finally, the proposed parameters for the engine were as shownin the table of FIG. 11 . The names of the proposed parameters accordingto the reference numerals are explained in the Features List whichfollows at the end of the detailed description section of thisspecification.

Following the selection of the proposed parameters, several iterationswere run using a detailed CFD modelling approach to assess and optimizethe flow guiding surfaces in the combustion system. After theseanalyses, the present applicant settled on an iteration showing a goodcompromise between charge motion and flow restriction.

FIG. 4 shows stationary port flow simulation results and FIG. 12 showscharge centering close to the centrally located spark plug. FIGS. 4 and12 show two important illustrations of the charge motion design process.FIG. 4 depicts the simulated intake flow field in the middle of theintake stroke in the valve cut-section of cylinder #1. It can be seenthat the applied high charge motion tumble intake port generates astrong jet of air flow entering the combustion chamber. Within thecombustion chamber, this jet is guided by the exhaust side of thecombustion chamber roof to transit into a tumble motion. The flatgeometry of the piston crown ensures low disturbances during intake andearly compression stroke. This enables a good conservation of the tumbleflow motion until the late phase of the compression cycle resulting in agood centering of the charge around the centrally located spark plug ascan be seen in FIG. 12 .

All the modelling performed on the engine was with RON 92 fuel. It wasdecided that this was an important consideration for a range extenderengine that would need to be flexible and be able to be fueled in eventhe most remote of locations.

FIG. 13 shows mass flow distribution over the two inlet valves.

When comparing the results of the engine analysis it is found that thechosen model iteration is located above the performance line of 30 othersimilar engines that were included in the FEV scatterband as shown inFIG. 14 (Evaluation of Charge motion vs engine scatterband). This provesa best-in-class trade-off between the flow performance is necessary toachieve the rated power and the charge motion resp. tumble to achievehigh efficiency in the entire engine map.

The table in FIG. 15 (Engine design attributes) shows a summary of theresulting technologies that were necessary to achieve the engineparameters that have been set for the engine performance. It can be seenthat the core of the proposed SYTECH engine family includes low cost,readily available technology features of common engines, such as fixedintake and exhaust camshaft timing (which is well suited fornon-transient REX applications), Port fuel injection and combinedCatalytic converter with GPF. As a result, this engine should be a lowcost engine with maximum reliability.

Although the engine architecture sounds relatively simple, according tothe modelling it is still able to achieve all of the design parametersset for the REX application. In addition, during the design and analysisstage, it was possible to incorporate space for a DI Injector and todesign the combustion chamber such as to protect for the future use of aTurbocharger with a common cylinder head base design. For any futureboosted application, the ports will have to be optimized for the TCapplication and machining for DI injector must also be considered butthe important note is that the cylinder head has been designed withthese options in mind. When we add these features to the enginesinherent size, shape, weight and vibration advantages, the applicant hasa good solution for range extender vehicles, particularly thoserequiring higher power outputs.

With relatively basic (common, state of the art) technology, we wereable to achieve an engine that was light weight, cost effective, lowrisk and with the ability to be fitted with a DI injector and/orturbo-charged at a later date with minimal changes.

The table in FIG. 16 shows performance vales of the 1.5 litre SYTECHengine and FIG. 17 shows engine performance. FIGS. 16 and 17 show themodelled performance results of ASFT's new 1.5 engine with 62 kW peakpower at 4500 RPM. As mentioned earlier, the engine is designed toprovide a high power output, Normally Aspirated even with RON 92 fuel.This target is represented by the peak torque of 140 Nm at 3000 rpmengine speed.

In order to realize this development, FEV and ASFT applied advancedengineering methods to ensure a fast, stable and efficient combustion,while maintaining low friction, good NVH and a lightweight design.

4 Engine Base Design

The base design of ASFT's new 1.5 l engine needs to be capable ofwithstanding the forces and loads generated by combustion whilst beingreliable, light-weight, low cost and low friction. Friction is a majorconsideration when designing an efficient engine. As the SYTECHpiston-to-crank connection is unique, during the FEV analysis andmodelling we had to assume a friction level that was based on previousSYTECH engines. The SYTECH engine should have a lower friction leveloverall as it has only 3 main bearings and two connecting Rod bearingsfor a 4 cylinder engine, as opposed to 5 main bearings and 4 connectingrod bearings as is the case for most conventional inline 4 cylinderengines. The SYTECH engine does have an additional slider bearing butthe slider bearing causes the piston to have almost no side forces sothe overall piston friction is lower. The focus of engine developmentafter the prototypes are built will be to tune the engine for emissionsand power, correlate the analysis models and analyse the overall enginefriction which will increase our efficiency and reduce our losses. Smallbearing diameters and a light-weight piston group with a low pre-tensionring pack help to reduce the friction in the crank train and havealready been included in the engine design.

For the timing drive, a belt has been chosen to combine the benefits ofexcellent robustness and a state-of-the-art NVH behavior and goodserviceability. At the same time, the layout of the complete timingdrive has been optimized in close cooperation with the belt drive systemsupplier to achieve a very low friction level and minimize beltharmonics and whipping.

The valve train uses roller finger followers (RFF) and hydraulic lashadjusters (HLA) for low friction and maintenance free operation. Thevalve spring design was analyzed and optimized in detail with kinematicand dynamic valve train simulations to ensure safe operation in thecomplete speed range. The balance shaft on the SYTECH engine runs atengine speed and this is directly chain driven off the crankshaft. Theoil pump is located around the crankshaft so that no drive relatedfriction losses need be considered.

5 Combustion Development

Several engines have been built and these are currently being prepared,instrumented and readied for testing at FEV's test facilities to verifythe concept, layout and design steps. The engine will be instrumentedwith water-cooled in-cylinder pressure transducers at all cylinders,exhaust and intake pressure indication at cylinder #1, comprehensiveexhaust gas analysis and thermocouples as well as pressure sensors atall relevant positions on the engine.

The combustion models used in the concept design study will be used forvalidation purposes and help further identify any areas for combustionsystem optimization following the first round of Thermodynamic testing.

6 Summary and Conclusion

ASFT Technologies Australia (ASFT) and FEV successfully cooperated inthe development of a new family of modern SYTECH gasoline engines. Thelead engine of this cooperative development is ASFT's new 1.5 litreopposed piston engine, which is designed for outstanding performance andgood fuel efficiency at a low cost using RON 92 fuel.

In order to achieve the targeted performance with RON 92 fuel, FEV andASFT focused on the development of a modern SYTECH engine with stablecombustion.

-   -   FEV's charge motion design process was successfully applied to        establish a high charge motion level, good flow conservation        until late compression and optimized turbulence localization at        end of the compression    -   The base engine was optimized to withstand the loads and forces        of combustion, while achieving a low weight, compact design and        low overall friction    -   The results from the modelling indicate that the SYTECH engine        should be a low cost solution, able to achieve China 6b with        minimal required technology.    -   The SYTECH engine approach results in a modular engine that can        be repeated in pairs of cylinders to achieve a family of engines        that share the same core design and components minimizing cost        and infrastructure.

ASFT's new engine family does not only provide outstanding performancewith minimal technology, but it has also been protected for theapplication of more sophisticated future technologies such as cooledEGR, Direct Injection and Turbocharging.

Therefore, the new 1.5 l SYTECH engine according to an example of theinvention is a Low Cost Unique solution for Modern Range Extenders.

Features List 10 Internal combustion engine 12 Cylinder 14 Piston 16Output shaft 18 Line of present engine (FIG. 2) 20 Line of conventionalengine (FIG. 2) 22 Line of present engine (FIG. 3) 24 Line ofconventional engine (FIG. 3) 26 Top Dead Centre 28 Bottom Dead Centre 30Combustion chamber 32 Valves 34 Both the present invention example“SYTech” and conventional engines have identical Stroke and Bore 36Conventional 38 SYTech 40 Before Top Dead Centre (TDC) 42 After Top DeadCentre (TDC) 44 Piston Velocity, mm/degree 46 Crank angle, degree 48Clearance Volume (CV) 50 Cylinder Volume 52 Swept Volume (CylinderCapacity) 54 Total Working Unit Cylinder Volume 56 Crank (degrees beforeTDC) 58 Crank angle, degree 60 % Combustion Chamber Velocity Difference(Conventional > SYTech), ((Conv. − SY)/CV)*100 62 Conventional 64Sinusoidal (SYTech) 66 % Conv. > SY, ((Conv. − SY)/SY)*100 68 Crank(degrees after TDC) 70 % Volume Difference 72 Sytech vs Conventional 74Arbitrary Section horizontal 76 Arbitrary Section vertical 78 Preview 80Section Valve 1 82 Section Valve 2 84 Preview 86 Connecting Rod 88Crankshaft 90 Slider Block 92 Piston 94 Conventional Engine 96 BoxerEngine 98 Many Imbalance Forces 100 Many Imbalance Forces 102 SYTechFlat Boxer Engine 104 Almost Nil Imbalance Forces 106 Smooth and QuietOperation with Perfect Balance 108 Conventional Engine at Full Load 110STTech Engine at Full Load 112 Acceleration (metres per second persecond) 114 Frequency (Hz) 116 Operation Noise Comparison: SYTech Engine75-80 db vs Conventional Engine 90-95 db 118 Wide Open Throttle CabinNoise, 2^(nd) Gear 120 Conventional Engine (4 Cylinder) 122 SYTech (4Cylinder) 124 Noise Level in db(A) 126 Engine Speed in RPM 128 Parameter130 No. of Cylinders 132 Engine Displacement 134 Power Estimate 136Stroke 138 Bore 140 Int. Angle 142 Int. Diameter 144 Exh. Angle 146 Exh.Diameter 148 Dv/D 150 CR 152 Sierra FEV-3 154 Sierra FEV-4 156TKE/m{circumflex over ( )}2/s{circumflex over ( )}2 158 CA = 720 degreesafter TDC 160 Outlet 162 Inlet 164 Outlet 166 Inlet 168 Massflowdistribution intake-valve-2/[kg/h] 170 Massflow distributionintake-valve-1/[kg/h] 172 Port flow coefficient 174 alpha K − 12.8% 176Evaluation of Charge Motion Generation 178 Required filling performance(rated power) 180 CMD trend line for IV angle 21 degrees, S/D 1.14 182Sierra FEV-2 184 Sierra FEV-4 186 Scatter NA 188 CMD trend line for IVangle 16 degrees, S/D 0.9, D 0.56 190 Flow coefficient (alpha K)/1 192First tumble peak/1 194 Engine technologies 196 Aluminium crankcase 198Forged steel crankshaft 200 Targeted lubrication 202 NVH optimisedbase-engine 204 NVH and friction optimised synchronous belt 206 Lowfriction roller finger follower valve train with maintenance freeautomatic hydraulic lash adjustment 208 Fixed intake and exhaust timing210 High charge motion tumble port 212 Port fuel injection 214 Closecoupled catalyst incl. GPF 216 Electric Water Pump 218 Optimised lowfriction piston rings 220 Balancer shaft (1^(st) order) 222 TechnologyProtections 224 Protection for external HP EGR 226 Protection forTurbo-charging 228 Protection for ISG 230 Protection for DirectInjection 232 SYTech 234 Performance Values of ASFT's 1.5 Liter engine236 Rated power @ 4500 rpm 238 Low end torque @ 1500 rpm 240 Specificpower output 242 Minimum BSFC @ 3020 rpm and 11.65 BMEP 244 Emissionlevel 246 Nominal fuel 248 Performance 250 New DoE 252 Old DoE 254 Brakepower/kW 256 BSFC/g/kW − h 258 Engine speed/rpm 260 Residual gasfraction/% 262 Brake torque/Nm 264 Cam lobes 266 Camshaft bearings 268Balance shaft 270 Camshaft 272 Balance shaft bearings (between camshaftand balance shaft) 274 Camshaft drive sprocket 276 Balance shaft drivesprocket 278 Slider bearing 280 Bolt 282 Slider bearing 284 Crankshaftbearing 286 Bolt 288 Angled slider block with in-interrupted sliderbearing faces using separate slider bearings 290 Slider bearing materialdeposited onto slider block 292 Bolt 294 Slider bearing materialdeposited onto slider block 296 Crankshaft bearing 298 Bolt 300 Angledslider block with un-interrupted slider bearing faces using directdeposited bearing material onto slider faces 302 Oil filter 304 Filteredoil being sent to engine bearings etc. 306 Pressurised oil 308 Oil pump310 Pressure regulator 312 Excess oil returned to Suction port 314Suction port 316 Oil Sump 318 Oil filter 320 Filtered oil being sent toengine bearings etc. 322 Pressurised oil 324 Oil pump 326 Pressureregulator 328 Two stage regulator diverts excess oil to piston sprays orother areas before returning oil to pump or sump 330 Then any additionalexcess oil is returned to Suction port or sump 332 Oil sump 334 Pistonsprays on slider block 336 Piston 338 Connecting rod 340 Slider block342 Connecting rod 344 Piston 346 Piston sprays in engine block that arefed from the two stage pressure regulator 348 Piston 350 Connecting rod352 Slider block 354 Connecting rod 356 Piston 358 Piston 360 Connectingrod 362 Slider block 364 Connecting rod 366 Piston 368 Piston sprays inengine block that are fed from excess oil from slider block. Sliderblock oil gallery aligns with spray nozzle and supplies oil to jet atthe top and bottom of each stroke (jets closed in this view) 370 Pistonsprays in engine block that are fed from excess oil from slider block.Slider block oil gallery aligns with spray nozzle and supplies oil tojet at the top and bottom of each stroke (top jet open in this view) 372Piston 374 Connecting rod 376 Slider block 378 Connecting rod 380 Piston382 Notches in edge of bearing faces (6 shown here) to allow oil to leakpast the thrust face and out the side of the bearing to lubricate thesides of the bearing and the associated thrust faces. This also appliesto the side of the crank flange faces 384 Slider bearing 386 Bolt 388Slider bearing 390 Crankshaft bearing 392 Bolt 394 Angled slider blockwith side notches in all bearings for side lubrication 396 Pre-setregulator in lube circuit 398 Oil filter 400 Filtered oil being sent toengine bearings etc. 402 Pre-set regulator 404 At a pre-set pressureflow, this regulator diverts filtered oil to the piston sprays etc. 406Main pressure regulator 408 Excess oil returned to Suction port 410 Oilsump 412 Pressurised oil 414 Oil pump 416 Typical Standard Valve 418Lube to engine parts 420 Filter 422 Pressure 424 Pump 426 Suction 428Oil strainer 430 Return 432 Oil sump 434 Regulator Valve 436 Two StageBlow-off 438 Lubrication to engine parts 440 Filter 442 Pressure 444Pump 446 Suction 448 Oil strainer 450 Oil sump 452 Return 454 To pistonjets (primary blow-off path) 456 Two stage regulator 458 Secondaryblow-off path 460 Blow-off (Intermediate) regulator 462 Lubrication toengine parts 464 Filter 466 Pressure 468 Pump 470 Suction 472 Oilstrainer 474 Oil sump 476 Return 478 Main regulator (45 psi) 480 Topiston jets etc 482 30 psi 484 Intermediate regulator 486 Twist 488Misalignment 490 Axial spacing 492 Pins allow for bore misalignment andtwist in all directions including crank to bore misalignment. Crankshaftshoulders allow piston connecting rods to self-centre 494 Guideshoulders on crank for slider bearing (both edges/sides of slider block)496 Axial spacing 498 Misalignment 500 Twist 502 Slider bearing sideguides in connecting rod 504 Guide shoulders on crank 506 Crank assembly508 Gear - crankshaft 510 Key 512 Crankshaft 514 Plug - crankshaft 516Pin - dowel 518 Trigger - wheel 520 Pin - dowel 522 Screw - triggerwheel 524 C-claw of connecting rod 526 Reverse C-claw of connecting rod528 Slider block components 530 Intake system 532 Injection system 534Cooling system 536 Cylinder head 538 Valve train 540 Timing drive 542Exhaust system 544 Colling system 546 Throttle body 548 Cylinder head550 Cylinder head 552 Cyclonic airflow in chamber 554 Air in 556 SYTechfiring order

The invention claimed is:
 1. An internal combustion engine having ahorizontally-opposed cylinder arrangement, including at least one pairof opposed pistons, respective cylinders associated with the pistons,and an output shaft, wherein each of the pistons is arranged forreciprocating motion within a respective one of the cylinders, driven bycombustion, and wherein the pistons are coupled to the output shaft by acoupling such that said reciprocating motion of the piston drivesrotation of the output shaft, wherein the coupling includes a connectingrod coupled to a respective pair of opposed pistons, a slider bearinglocated for reciprocating movement relative to the connecting rod, thecoupling further including a crankshaft that is rotatably mounted withinthe slider bearing, the engine having a camshaft and a balance shaftwherein the balance shaft is housed in a hollow of the camshaft suchthat the camshaft and the balance shaft rotate about a common axis. 2.An internal combustion engine as claimed in claim 1, wherein theconnecting rod is of unitary construction.
 3. An internal combustionengine as claimed in claim 1, wherein the balance shaft is driven at thesame speed as a speed of the crankshaft.
 4. An internal combustionengine as claimed in claim 1, wherein the engine is provided with asingle balance shaft.
 5. An internal combustion engine as claimed inclaim 1, wherein the camshaft rotates at half the speed of thecrankshaft.
 6. An internal combustion engine as claimed in claim 1,wherein the camshaft and balance shaft are pre-assembled as a moduleprior to assembly in the engine.
 7. An internal combustion engine asclaimed in claim 1, wherein the camshaft and the balance shaft arearranged to rotate in a common rotational direction.
 8. An internalcombustion engine as claimed in claim 7, wherein the balance shaft ismounted relative to the camshaft by at least one bearing fitted betweenthe balance shaft and the camshaft.
 9. An internal combustion engine ofclaim 8, wherein the balance shaft is mounted relative to the camshaftby a plurality of balance shaft bearings that are spaced along thehollow of the camshaft.
 10. An engine as claimed in claim 1, wherein thecoupling is arranged such that the piston has sinusoidal motion forconstant rotational velocity of the output shaft when plotted againstrotational angle of the output shaft.
 11. An engine as claimed in claim10 wherein the engine is in the form of a scotch yoke engine.
 12. Anengine as claimed in claim 1, wherein the engine is arranged such that,when measured against a conventional crankshaft engine of identical boreand stroke, the motion of the piston after top dead centre has a loweracceleration such that volumetric difference in the cylinder, whencompared to the conventional crankshaft engine, peaks at between 10% and20% between top dead centre and bottom dead centre.
 13. An engine asclaimed in claim 12, wherein the engine is arranged such that, whenmeasured against a conventional crankshaft engine of identical bore andstroke, the motion of the piston after top dead centre has a loweracceleration such that volumetric difference in the cylinder peaks atbetween 40 and 80 degrees of output shaft rotation after top deadcentre.
 14. An engine as claimed in claim 12, wherein the engineincludes a combustion chamber, and wherein the combustion chamber and/orthe coupling are arranged to achieve goal volumetric differencecharacteristics.
 15. A method of manufacturing an engine as claimed inclaim 1, including: measuring and/or modelling charge density in thecylinder to obtain data; and using said data to optimise one or moreparameter(s) of the engine so as to increase maintenance of a gas statewith a higher charge density around top dead centre to achieve improvedfuel mixing.
 16. A method of manufacturing an engine as claimed in claim15, including the step of using said data to optimise one or moreparameter(s) of the engine, said parameter(s) including one or more ofthe coupling, the piston, the cylinder, a combustion chamber, andvalves.
 17. An internal combustion engine of claim 9, wherein aplurality of camshaft bearings are arranged around the camshaft, thecamshaft bearings being axially aligned along the camshaft with thebalance shaft bearings.
 18. An internal combustion engine as claimed inclaim 1, wherein the balance shaft and the camshaft each have arespective sprocket that is arranged to be driven by the crankshaft. 19.An internal combustion engine as claimed in claim 1, wherein the balanceshaft is chain driven off the crankshaft.
 20. An internal combustionengine as claimed in claim 1, wherein the camshaft and balance shaft arearranged to spin in contra-rotation.